Polyurethane foams are produced by the reaction of polyisocyanates and polyols in the presence of a blowing agent. In order to improve load-bearing and other foam properties, so-called polymer polyol products have been developed. A common type of polymer polyol is a dispersion of vinyl polymer particles in a polyol. Examples of vinyl polymer particle polyols include so-called “SAN” polyols, which are dispersions of styrene-acrylonitrile. Other common types of polymer polyols are so-called “PHD” polyols (dispersions of polyurea particles) and so-called “PIPA” (polyisocyanate polyaddition) polyols (dispersions of polyurethane and/or polyurethane-urea particles). PIPA and PHD particles may be produced by introducing the appropriate co-reactant or co-reactants into a polyol or polyol blend and reacting the co-reactant(s) with a polyisocyanate in order to polymerize the co-reactant(s) in the presence of a tin salt catalyst such as for example stannous octoate, dimethyltin, and dibutyltin catalysts. However, there is a desire to reduce the use of tin based catalysts.
Therefore, there is a need for polymer polyols made with using less tin based catalysts, or without any tin based catalyst.